Electronic blood pressure monitor

ABSTRACT

An electronic blood pressure monitor of the present invention includes a blood pressure measurement cuff that is to be worn on a measurement site of a measurement subject. The electronic blood pressure monitor includes a blood pressure measurement unit that measures a blood pressure value of the measurement subject using the cuff. The electronic blood pressure monitor includes an external compression detection unit that detects whether or not there was external compression on the cuff during blood pressure measurement performed by the blood pressure measurement unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of International Application No.PCT/JP2016/079314, with an International filing date of Oct. 3, 2016,which claims priority of Japanese Patent Application No. 2015-257066filed on Dec. 28, 2015, the entire content of which is herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to an electronic blood pressure monitor,and more specifically relates to an electronic blood pressure monitorthat includes a cuff worn on a measurement site of a measurementsubject, and that increases the pressure of the cuff by supplying afluid thereto to compress the measurement site and perform bloodpressure measurement.

BACKGROUND ART

Conventionally, as this type of electronic blood pressure monitor, asdisclosed in Patent Document 1 (JP 2008-188197A) for example, anelectronic blood pressure monitor is known in which, upon being startedup, air is supplied to a cuff, pressure increase is started, and basedon the extent of the increase in the pressure in the cuff, it isdetermined whether or not the cuff is being worn appropriately on ameasurement site such as an upper arm.

SUMMARY OF INVENTION

Incidentally, in recent years, the importance of measuring night-timeblood pressure for treatment of hypertension has been receivingattention. In night-time blood pressure measurement, blood pressuremeasurement is generally performed automatically using a timer settingduring a sleep period of the measurement subject, and therefore themeasurement subject cannot consciously correct his or her orientationduring blood pressure measurement. For this reason, blood pressurevalues obtained in various orientations can be recorded. For example, ifthe measurement subject, who is lying on a bed surface, places the cuff,which is worn on the upper arm (measurement site), under his or hertorso, the cuff will be compressed from the outside (the torso and thebed surface), and therefore there is a possibility that the recordedblood pressure value will be influenced. Accordingly, it is convenientif a user (includes a medical professional such as a doctor or a nurse,for example, in addition to the measurement subject; the same applies inthe following description) can later check whether or not there wascompression from the outside (external compression) on the cuff duringblood pressure measurement.

However, as far as the applicants of the present application know, anelectronic blood pressure monitor according to which a user can checkwhether or not there was external compression on a cuff during bloodpressure measurement has not conventionally existed.

In view of this, the present invention aims to provide a blood pressuremonitor according to which a user can check whether or not there wasexternal compression on the cuff during blood pressure measurement.

In order to solve the above-described problem, the electronic bloodpressure monitor of this disclosure includes:

a blood pressure measurement cuff configured to be worn on a measurementsite of a measurement subject;

a blood pressure measurement unit configured to measure a blood pressurevalue of the measurement subject using the cuff; and

an external compression detection unit configured to detect whether ornot there was external compression on the cuff during the blood pressuremeasurement performed by the blood pressure measurement unit, wherein ineach predetermined pressure segment, the external compression detectionunit calculates a cuff compliance, which is an amount of air that is tobe pumped into the cuff and is needed to increase pressure in the cuffper unit pressure, as the pressure of the cuff is increased by the bloodpressure measurement unit during blood pressure measurement, and theexternal compression detection unit determines whether or not there isexternal compression on the cuff based on a change indicated by the cuffcompliance in each pressure segment.

In the present specification, “during blood pressure measurement” doesnot indicate the entire period in which the blood pressure measurementcuff is worn for night-time blood pressure measurement and the like, forexample, but indicates a timing during which the blood pressure valuesof the measurement subject are measured by actually increasing orreducing the pressure of the above-described blood pressure measurementcuff.

Also, “external compression” indicates compression from the outside ofthe external circumferential surface of the blood pressure monitor thatis wrapped around the measurement site. In other words, “externalcompression” does not encompass compression from the measurement site(inner circumferential surface side of the cuff) around which the bloodpressure measurement cuff is wrapped. Typically, external compressionoccurs when the measurement subject lying on the bed surface places thecuff worn on the measurement site under the torso in the case ofnight-time blood pressure measurement. Note that “bed surface” widelyindicates a surface on which a measurement subject can lie, such as anupper surface of a bed or futon. The torso of the measurement subjectmay be wearing clothes.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a schematic view showing an exterior of a blood pressuremonitor in which the cuff and the main body are integrated, and in whicha blood pressure related information display apparatus according to anembodiment of the invention is included.

FIG. 2 is a diagram showing a block configuration of the blood pressuremonitor.

FIG. 3 is a diagram showing a block configuration of a hospital terminalthat can communicate with the blood pressure monitor via a network.

FIG. 4A is a diagram showing a state in which the measurement subjectwears the blood pressure monitor on a left upper arm serving as ameasurement site and is in a supine orientation (supine position) on abed surface. FIG. 4B is a diagram showing a state in which themeasurement subject has changed the torso angle with respect to the bedsurface from the state of FIG. 4A.

FIG. 5 is a diagram showing an overall operation flow of the bloodpressure monitor.

FIG. 6A is a diagram illustrating a cuff pressure signal, a pulse wavesignal, a pump driving signal, and a cuff compliance during bloodpressure measurement (pressure increase process) in the case where thereis no external compression on the cuff of the blood pressure monitor.

FIG. 6B is a diagram illustrating a cuff pressure signal, a pulse wavesignal, a pump driving signal, and a cuff compliance during bloodpressure measurement (pressure increase process) in the case where thereis external compression on the cuff of the blood pressure monitor (here,a case in which the cuff is placed under the torso of the measurementsubject).

FIG. 7 is a diagram illustrating the output of an acceleration sensorbuilt in the main body, during blood pressure measurement performed bythe blood pressure monitor.

FIG. 8A is a diagram showing a correspondence relationship between theorientation (torso angle and arm position) of the measurement subjectduring blood pressure measurement and the outputs (XZ coordinates and XYcoordinates) of the acceleration sensor.

FIG. 8B is a diagram showing a correspondence relationship between theorientation (torso angle and arm position) of the measurement subjectduring blood pressure measurement and the outputs (XZ coordinates and XYcoordinates) of the acceleration sensor.

FIG. 8C is a diagram showing a correspondence relationship between theorientation (torso angle and arm position) of the measurement subjectduring blood pressure measurement and the outputs (XZ coordinates and XYcoordinates) of the acceleration sensor.

FIG. 8D is a diagram showing a correspondence relationship between theorientation (torso angle and arm position) of the measurement subjectduring blood pressure measurement and the outputs (XZ coordinates and XYcoordinates) of the acceleration sensor.

FIG. 8E is a diagram showing a correspondence relationship between theorientation (torso angle and arm position) of the measurement subjectduring blood pressure measurement and the outputs (XZ coordinates and XYcoordinates) of the acceleration sensor.

FIG. 8F is a diagram showing a correspondence relationship between theorientation (torso angle and arm position) of the measurement subjectduring blood pressure measurement and the outputs (XZ coordinates and XYcoordinates) of the acceleration sensor.

FIG. 8G is a diagram showing a correspondence relationship between theorientation (torso angle and arm position) of the measurement subjectduring blood pressure measurement and the outputs (XZ coordinates and XYcoordinates) of the acceleration sensor.

FIG. 8H is a diagram showing a correspondence relationship between theorientation (torso angle and arm position) of the measurement subjectduring blood pressure measurement and the outputs (XZ coordinates and XYcoordinates) of the acceleration sensor.

FIGS. 9A and 9B are diagrams illustrating images to be displayed on adisplay device of the blood pressure monitor.

FIGS. 10A and 10B are diagrams illustrating images to be displayed onthe display device of the blood pressure monitor.

FIG. 11 is a diagram showing portions of the overall operation flow(portions relating to detection of external compression) of FIG. 5.

FIG. 12 is a diagram showing a specific flow of cuff compliancecalculation processing shown in FIG. 11.

FIG. 13 is a diagram showing a specific flow of cuff pressure existencedetection processing shown in FIG. 11.

FIG. 14A is a diagram showing a change in the compliance ratioaccompanying a change in the cuff pressure during blood pressuremeasurement (pressure increase process) in the case where there is noexternal compression on the cuff.

FIG. 14B is a diagram showing a change in the compliance ratioaccompanying a change in the cuff pressure during blood pressuremeasurement (pressure increase process) in the case where there isexternal compression on the cuff (here, in the case where the cuff isplaced under the torso of the measurement subject).

FIG. 15 is a diagram illustrating an image to be displayed on thedisplay device of the hospital terminal.

FIG. 16 is a diagram illustrating another image to be displayed on thedisplay device of the hospital terminal.

FIG. 17 is a diagram illustrating yet another image to be displayed onthe display device of the hospital terminal.

DESCRIPTION OF EMBODIMENTS

Configuration of Blood Pressure Monitor

FIG. 1 shows an exterior of an electronic blood pressure monitor(indicated overall by reference numeral 1) according to an embodiment ofthe invention.

The blood pressure monitor 1 mainly includes a blood pressuremeasurement cuff 20 that is to be wrapped around a measurement site of ameasurement subject, and a main body 10 that is integrally attached tothe cuff 20.

The cuff 20 has a shape that is elongated so as to wrap around themeasurement site along the circumferential direction, and includes aband-shaped inner cloth 20 a that is to come into contact with themeasurement site, and an outer cloth 20 b that opposes the inner cloth20 a. The inner cloth 20 a and the outer cloth 20 b are formed into abladder shape by having their peripheral edges sewn together. The cuff20 contains a fluid bladder 22 (see FIG. 2) for compressing ameasurement site.

In order to form a surface fastener, the surface (inner circumferentialsurface that is to come into contact with the measurement site) of theinner cloth 20 a is provided with many minute hooks (not shown). On theother hand, many minute loops (not shown) that engage with theabove-described hooks are formed on the surface (outer circumferentialsurface) of the outer cloth 20 b.

The main body 10 is integrally attached to a site between one end (endportion that is to serve as the inner circumferential end when worn) 20e and another end (end portion that is to serve as the outercircumferential end when worn) 20 f with respect to the lengthwisedirection (circumferential direction) of the cuff 20.

When the blood pressure monitor 1 is worn on the left upper arm 90 a(see FIG. 4A) serving as the measurement site, the left upper arm 90 ais arranged in the orientation indicated by the arrow A in FIG. 1 andthe cuff 20 is arranged along with the main body 10 on the front surfaceof the left upper arm 90 a. Next, the cuff 20 is wrapped in the form ofa left-handed spiral as viewed by the measurement subject. Then, thecorresponding surface of the inner cloth 20 a is pressed onto and fixedto a site near the inner circumferential end 20 e compared to the mainbody 10 of the outer cloth 20 b. The extra portion near the other end 20f in the lengthwise direction (circumferential direction) of the cuff 20is folded over so as to prevent the main body 10 from being hidden.

FIG. 2 shows a schematic block configuration of the cuff 20 and the mainbody 10 of the blood pressure monitor 1. The blood pressure monitor 1includes a CPU (Central Processing Unit) 100 serving as a control unit,a display device 50, an operation unit 52, a memory 51 serving as astorage unit, a communication unit 59, a power source unit 53, a pump32, a valve 33, a pressure sensor 31, and an acceleration sensor 34, allof which are mounted in the main body 10. Furthermore, the main body 10includes an oscillation circuit 310 that converts the output from thepressure sensor 31 into a frequency, a pump driving circuit 320 thatdrives the pump 32, a valve driving circuit 330 that drives the valve33, and an AD converter 340 that performs AD (Analog to Digital)conversion on the output from the acceleration sensor 34, all of whichare mounted in the main body 10.

In this example, the display device 50 is composed of an LCD (LiquidCrystal Display) and displays information relating to blood pressure,such as a blood pressure measurement result, in accordance with acontrol signal from the CPU 100.

The operation unit 52 includes a power source switch 52A for turning onand off the power source of the main body 10, a measurement start switch52B for receiving an instruction to start blood pressure measurement,and a memory switch 52C for calling a blood pressure measurement resultstored in the memory. The switches 52A, 52B, and 52C input operationsignals corresponding to instructions performed by a user to the CPU100.

As shown in FIG. 1, the display device 50 and the operation unit 52 areprovided on the front surface (upper surface in FIG. 1) or the sidesurface of the main body 10.

The memory 51 shown in FIG. 2 stores data of programs for controllingthe blood pressure monitor 1, data to be used to control the bloodpressure monitor 1, setting data for setting various functions of theblood pressure monitor 1, data of measurement results of blood pressurevalues, data indicating whether or not there is later-described externalcompression on the cuff 20, whether or not there is bodily movement of ameasurement subject, and the orientation of the measurement subject, andthe like. Also, the memory 51 is used as a work memory or the like forwhen a program is executed.

In accordance with a program for controlling the blood pressure monitor1 that is stored in the memory 51, the CPU 100 performs control fordriving the pump 32 and the valve 33 according to the operation signalfrom the operation unit 52. Also, based on a signal from the pressuresensor 31, the CPU 100 performs control for calculating the bloodpressure values and control for detecting whether or not there isexternal compression on the cuff 20. Furthermore, based on the output ofthe acceleration sensor 34, the CPU 100 performs control for detectingwhether or not there is bodily movement of the measurement subject andthe orientation of the measurement subject. These controls will bedescribed in detail later.

The communication unit 59 is controlled by the CPU 100 to transferpredetermined information to an external apparatus via the network 900,and to receive information from the external apparatus via the network900 and transfer it to the CPU 100. Communication via the network 900may be performed wirelessly or using a wire. In this embodiment, thenetwork 900 is the Internet, but there is no limitation to this, and itis also possible to use another type of network such as an in-hospitalLAN (Local Area Network), or one-to-one communication using a USB cableor the like.

The power source unit 53 supplies power to the units, namely the CPU100, the pressure sensor 31, the pump 32, the valve 33, the accelerationsensor 34, the display device 50, the memory 51, the communication unit59, the oscillation circuit 310, the pump driving circuit 320, the valvedriving circuit 330, and the AD converter 340.

The pump 32, the valve 33, and the pressure sensor 31 are connected tothe fluid bladder 22 contained in the cuff 20 via a common air tube 39serving as a tube system. The pump 32 supplies air to the fluid bladder22 through the air tube 39 in order to increase the pressure (cuffpressure) in the fluid bladder 22 contained in the cuff 20. The valve 33is a solenoid valve that is controlled so as to open and close throughapplication of a current, and is used to control the cuff pressure bydischarging the air in the air bladder 22 through the air tube 39 orsealing the air in the air bladder 22. The pump driving circuit 320drives the pump 32 based on the control signal provided by the CPU 100.The valve driving circuit 330 opens and closes the valve 33 based on thecontrol signal provided from the CPU 100.

In this example, the pressure sensor 31 is a piezoresistance pressuresensor that detects the pressure of the cuff 20 (fluid bladder 22)through the air tube 39, and in this example, the pressure sensor 31detects a pressure obtained with reference to atmospheric pressure (withatmospheric pressure being set to zero) and outputs the detectedpressure as a cuff pressure signal Pc in a time series. The oscillationcircuit 310 oscillates based on an electricity signal value that isbased on a change in the electric resistance caused by a piezoresistanceeffect from the pressure sensor 31, and outputs a frequency signalhaving a frequency corresponding to the electricity signal value of thepressure sensor 31 to the CPU 100.

In this example, the output of the pressure sensor 31 is used tocalculate the blood pressure values (includes systolic blood pressureand diastolic blood pressure; the same applies in the descriptionhereinafter) of the measurement subject 90 through an oscillomerticmethod. In addition to this, the output of the pressure sensor 31 isused to determine whether or not there is external compression on thecuff 20 by calculating the cuff compliance (amount of air needed tochange the cuff pressure by a unit pressure 1 mmHg). Typically, in thecase of night-time blood pressure measurement, external compressionoccurs when the cuff 20 and the left upper arm 90 a serving as themeasurement site are placed under the torso of the measurement subjectwho is lying down, and are compressed by the torso and the bed surface.

The acceleration sensor 34 is composed of a triaxial acceleration sensorthat is integrally built into the main body 10. The acceleration sensor34 outputs an acceleration signal indicating acceleration in threemutually orthogonal directions of the main body 10 and accordingly, ofthe cuff 20 integrally attached to the main body 10, to the CPU 100 viathe AD converter 340.

In this example, as shown in FIG. 4A, an XYZ orthogonal coordinatesystem is set with the position of the acceleration sensor 34 in themain body 10 serving as the origin. The Z axis is set facing outwardorthogonally to the front surface of the main body 10. The Y axis is setin an orientation facing from the knee to the shoulder along the leftupper arm 90 a of the measurement subject 90 in a state in which theblood pressure monitor 1 is worn on the left upper arm 90 a serving asthe measurement site as described above. Also, the X axis is setorthogonally to the Y axis and the Z axis (the X axis facesapproximately leftward as viewed by the measurement subject 90, but thisdepends on the orientation of the measurement subject 90 as well). Notethat in FIG. 4A, the measurement subject 90 is in a supine orientation(supine position) on the bed surface 99, but in actuality, especially inthe case of night-time blood pressure measurement, the measurementsubject 90 can be in various orientations. For example, as shown in FIG.4B, the measurement subject can be in an orientation in which the angleθ of the torso is changed with respect to the bed surface 99.

In this example, the output of the acceleration sensor 34 is used todetect whether or not there is bodily movement of the measurementsubject 90. In addition, the output of the acceleration sensor 34 isused to detect the orientation of the measurement subject 90 accordingto the direction (e.g., in FIGS. 4A and 4B, the directions of thegravity acceleration vectors G with respect to the XYZ orthogonalcoordinate system are different) of a gravity acceleration vector G withrespect to the above-described XYZ orthogonal coordinate system.

Method of Detecting External Compression

FIG. 6A shows a cuff pressure signal Pc, a pulse wave signal SM, a pumpdriving signal Vout, and a cuff compliance CL during blood pressuremeasurement (pressure increase process) in the case where there is noexternal compression on the cuff 20. On the other hand, FIG. 6B shows acuff pressure signal Pc, a pulse wave signal SM, a pump driving signalVout, and a cuff compliance CL during blood pressure measurement(pressure increase process) in the case where there is externalcompression on the cuff 20 (here, a case in which the cuff 20 is placedunder the torso of the measurement subject 90). The cuff pressure signalPc indicates the pressure of the cuff 20 (fluid bladder 22) that isdetected via the air tube 39 and the oscillation circuit 310 by thepressure sensor 31. The pulse wave signal SM indicates a signalextracted through a filter (not shown) as a fluctuation component of thecuff pressure signal Pc (the pulse wave signal SM is used to calculatethe blood pressure values through an oscillometric method). The pumpdriving signal Vout indicates a square wave signal (pulse widthmodulation signal) output from the CPU 100 to the pump driving circuit320 in order to increase the pressure of the cuff 20. The cuffcompliance CL is obtained as values (calculated for each predeterminedpressure segment) CMa, CMb, CMc, CMd, . . . , which are obtained byintegrating the duty of the pump driving signal Vout over time. In orderto facilitate understanding, in FIGS. 6A and 6B, an envelope EV is addedto the sequence formed by the values CMa, CMb, CMc, CMd, . . . of thecuff compliance CL.

As can be understood from FIG. 6A, if there is no external compressionon the cuff 20, air is supplied to the cuff 20, and the cuff complianceCL gradually decreases and is saturated as pressure increase from thelow pressure range (0 mmHg to less than 40 mmHg) to the high pressurerange (over 120 mmHg) is performed. The reason for this is because ifthere is no external compression on the cuff 20, the volume of the cuffeasily expands in the low pressure region (0 mmHg to less than 40 mmHg),and therefore a large amount of air is needed to raise the cuffpressure, but the volume of the cuff 20 is substantially less likely toincrease when the tensile force of the cuff 20 increases due to the cuffpressure rising by a certain degree. On the other hand, as can beunderstood from FIG. 6B, if there is external compression on the cuff20, the cuff compliance CL has a maximum value in the pressure increaseprocess. In this case, in the low pressure region (0 mmHg to less than40 mmHg), the volume of the cuff 20 increases due to the cuff 20pressing back on the torso of the measurement subject 90. Accordingly,the cuff compliance CL changes gradually from a low value (varies due tothe influence of the tensile force of wrapping the cuff around themeasurement site) to a high value. On the other hand, in the highpressure region (over 120 mmHg), the torso is pushed away by the top ofthe cuff 20 due to the inflation of the cuff 20, and therefore the cuffcompliance CL gradually decreases and is saturated, similarly to thecase shown in FIG. 6A (the case in which there is no externalcompression). As a result, in the intermediate range (40 mmHg or more,120 mmHg or less), the cuff compliance CL has a maximum valueaccompanying the rising of the cuff pressure.

Accordingly, it is possible to detect whether or not there is externalcompression on the cuff 20 according to whether or not the cuffcompliance CL has a maximum value in the intermediate pressure range (40mmHg or more and 120 mmHg or less) in the pressure increase process.

Method of Detecting Bodily Movement

FIG. 7 illustrates the outputs (acceleration signals) of theacceleration sensor 34 during blood pressure measurement. During bloodpressure measurement, and especially during night-time blood pressuremeasurement, the measurement subject 90 is essentially in a restingstate, and therefore an output α_(x) in the X-axis direction of theacceleration sensor 34, an output α_(y) in the Y-axis direction, and anoutput α_(z) in the Z-axis direction have approximately constant values.However, if the measurement subject 90 temporarily moves by turning overor the like, the outputs α_(x), α_(y), and α_(z) change as indicated byα_(x)1, α_(y)1, and α_(z)1.

In this example, the CPU 100 functions as a bodily movement detectionunit, and during blood pressure measurement, obtains average values<α_(x)>, <α_(y)>, and <α_(z)> of the outputs αx, α_(y), and α_(z) of theacceleration sensor 34 in each unit period (e.g., one second or severalseconds). Furthermore, the CPU 100 obtains fluctuation amounts(α_(x)−<α_(x)>), (α_(y)−<α_(y)>), and (α_(z)−<α_(z)>) by which theacceleration outputs α_(x), α_(y), and α_(z) of the times in the unitperiod fluctuate with respect to the average values <α_(x)>, <α_(y)>,and <α_(z)>. Also, when the square root of the sum of squares of thesefluctuation amounts{(α_(x)−<α_(x)>)²+(α_(y)−<α_(y)>)²+(α_(z)−<α_(z)>)²}^(1/2)exceeds a predetermined threshold (denoted as Δα), it is determined thatthere is bodily movement. On the other hand, if the square root of thesum of the squares is less than or equal to the threshold Δα, it isdetermined that there is no bodily movement.

Accordingly, it is possible to detect whether or not there is bodilymovement of the measurement subject 90 based on changes in the outputsof the acceleration sensor 34.

Method of Detecting Orientation

FIGS. 8A to 8H show correspondence relationships between the orientation(torso angle and arm position) of the measurement subject 90 duringblood pressure measurement and the normalized outputs (XZ coordinatesand XY coordinates) of the acceleration sensor 34.

Specifically, FIGS. 8A to 8H show eight types of “torso angles” as torsopatterns in the first rows (top rows). “Torso angle” means the angle(indicated by reference numeral θ in FIG. 4B) by which the flat torso 90b is rotated about a center (approximately matches the spine) in a viewalong the body height direction (in this example, in a view from head tofeet) of a person lying on a bed surface. In FIG. 8A, the torso 90 b isin the supine position and the torso angle is 0 degrees. In FIG. 8B, thetorso 90 b is between the supine position and the right side position,and the torso angle is 20 degrees. In FIG. 8C, the torso 90 b is in theright side position and the torso angle is 90 degrees. In FIG. 8D, thetorso 90 b is between the right side position and the prone position,and the torso angle is 160 degrees. In FIG. 8E, the torso 90 b is in theprone position and the torso angle is 180 degrees. In FIG. 8F, the torso90 b is between the prone position and the left side position, and thetorso angle is 200 degrees. In FIG. 8G, the torso 90 b is in the leftside position and the torso angle is 270 degrees. In FIG. 8H, the torso90 b is between the left side position and the supine position, and thetorso angle is 340 degrees.

Also, in FIGS. 8A to 8H, the second rows each show four or three typesof representative arm positions serving as arm patterns corresponding toarm positions that are varied with respect to a person's torso. In FIG.8A, in the first column (leftmost column), the left upper arm 90 a is ata “body-lateral” position of extending along the lateral side of thetorso 90 b, in the second column, the left upper arm 90 a is at a“body-side separated” position of being separated laterally from thetorso 90 b, in the third column, the left upper arm 90 a is at an“on-chest” position of being placed on the torso 90 b, and in the fourthcolumn (rightmost column), the left upper arm 90 a is in a “hurrah”position of being raised toward the head. In FIGS. 8B, 8C, and 8D, inthe first columns (leftmost columns), the left upper arm 90 a is at a“back-side” position of being rotated rearward of the torso 90 b, in thesecond columns, the left upper arm 90 a is at a “body-lateral” positionof extending along the lateral side of the torso 90 b, in the thirdcolumns, the left upper arm 90 a is at a “chest-side” position of beingrotated frontward of the torso 90 b, and in the fourth columns(rightmost columns), the left upper arm 90 a is at a “hurrah” positionof being raised toward the head. In FIG. 8E, in the first column(leftmost column), the left upper arm 90 a is at a “body-lateral”position of extending along the lateral side of the torso 90 b, in thesecond column, the left upper arm 90 a is at a “body-side separated”position of being separated laterally from the torso 90 b, and in thethird column, (rightmost column), the left upper arm 90 a is in a“hurrah” position of being raised toward the head. In FIG. 8F, in thefirst column (leftmost column), the left upper arm 90 a is at a“back-side” position of being rotated rearward of the torso 90 b, in thesecond column, the left upper arm 90 a is at a “body-lateral” positionof extending along the lateral side of the torso 90 b, and in the thirdcolumn (rightmost column), the left upper arm 90 a is at a position ofbeing rotated frontward of the torso 90 b. In FIG. 8G, in the firstcolumn (leftmost column), the left upper arm 90 a is at a “chest-frontseparated” position of being separated frontward from the torso 90 b, inthe second column, the left upper arm 90 a is at a “body-lateral”position of extending along the lateral side of the torso 90 b, and inthe third column (rightmost column), the left upper arm 90 a is at a“hurrah” position of being raised toward the head. Also, in FIG. 8H, inthe first column (leftmost column), the left upper arm 90 a is at a“chest-front” position of being rotated frontward from the torso 90 b,in the second column, the left upper arm 90 a is at a “body-lateral”position of extending along the lateral side of the torso 90 b, and inthe third column (rightmost column), the left upper arm 90 a is at a“hurrah” position of being raised toward the head.

The orientations of the measurement subject 90 during blood pressuremeasurement (in particular, during night-time blood pressuremeasurement) are specified using combinations of the “torso angles” inthe first rows (top rows) and the “arm positions” in the second rowscorresponding thereto in FIGS. 8A to 8H.

In the third rows and the fourth rows (bottom rows) in FIGS. 8A to 8H,the normalized (normalized to 1) outputs of the acceleration sensor 34in cases where the measurement subject 90 is in orientations specifiedusing combinations of the “torso angles” in the first rows and the “armpositions” in the second rows are indicated in XZ coordinate planes andXY coordinate planes. Here, the measurement subject 90 is substantiallyin a resting state, and the outputs (the above-described average values<α_(x)>, <α_(y)>, and <α_(z)>) of the acceleration sensor 34 correspondto the direction of the gravity acceleration vector G corresponding tothe XYZ orthogonal coordinate system set in the main body 10.

For example, if the measurement subject 90 is in an orientationspecified using a combination in which the “torso angle” is 0 degreesand the “arm position” is “body-lateral” in the first column (leftmostcolumn) of FIG. 8A, the normalized outputs of the acceleration sensor 34are detected as point a_(xz) where X=0 and Z=1 in the XZ coordinateplane in the third row, and as point a_(xy) where X=0 and Y=0 in the XYcoordinate plane in the fourth row. Also, when the measurement subject90 is in an orientation specified using the combination in which the“torso angle” is 0 degrees and the “arm position” is “body-sideseparated” in the second column of FIG. 8A, the normalized outputs ofthe acceleration sensor 34 are detected as point a_(xz) where −1<X<0 and0<Z<1 (second quadrant) in the XZ coordinate plane in the third row, andas point a_(xy) where −1<X<0 and Y=0 in the XY coordinate plane in thefourth row. When the measurement subject 90 is in an orientationspecified using the combination in which the “torso angle” is 0 degreesand the “arm position” is “on-chest” in the third column of FIG. 8A, thenormalized outputs of the acceleration sensor 34 are detected as pointa_(xz) where 0<X<1 and 0<Z<1 (first quadrant) in the XZ coordinate planein the third row, and as point a_(xy) where 0<X<1 and −1<Y<0 (fourthquadrant) are satisfied in the XY coordinate plane in the fourth row.When the measurement subject 90 is in an orientation specified using thecombination in which the “torso angle” is 0 degrees and the “armposition” is “hurrah” in the fourth column (rightmost column) of FIG.8A, the normalized outputs of the acceleration sensor 34 are detected aspoint a_(xz) where −1<X<0 and −1<Z<0 (third quadrant) in the XZcoordinate plane in the third row, and as point a_(xy) where −1<X<0 and−1<Y<0 (third quadrant) in the XY coordinate plane in the fourth row.

Also, for example, if the measurement subject 90 is in an orientationspecified using the combination in which the “torso angle” is 270degrees and the “arm position” is “chest-front separated” in the firstcolumn (leftmost column) in FIG. 8G, the normalized outputs of theacceleration sensor 34 are detected as point a_(xz) where X=−1 and Z=0in the XZ coordinate plane in the third row, and as point a_(xy) whereX=−1 and Y=0 in the XY coordinate plane in the fourth row. Also, if themeasurement subject 90 is in an orientation specified using thecombination in which the “torso angle” is 270 degrees and the “armposition” is “body-lateral” in the second column in FIG. 8G, thenormalized outputs of the acceleration sensor 34 are detected as pointa_(xz) where X=−1 and Z=0 in the XZ coordinate plane in the third row,and as point a_(xy) where X=−1 and Y=0 in the XY coordinate plane in thefourth row. If the measurement subject 90 is in an orientation specifiedusing the combination in which the “torso angle” is 270 degrees and the“arm position” is “hurrah” in the third column (rightmost column) inFIG. 8G, the normalized output of the acceleration sensor 34 is detectedas point a_(xz) where 0<X<1 and 0<Z<1 (first quadrant) in the XZcoordinate plane in the third row, and as point a_(xy) where 0<X<1 andY=0 in the XY coordinate plane in the fourth row.

As can be understood from the examples above, in FIGS. 8A to 8H, whenthe measurement subject 90 is in an orientation specified using acombination of a “torso angle” in a first row and an “arm position” in asecond row, the orientation and the normalized output (combination of XZcoordinates and XY coordinates) of the acceleration sensor 34 are in aone-to-one correspondence. Accordingly, if the normalized outputs(combination of the XZ coordinates and the XY coordinates) of theacceleration sensor 34 are specified, the orientation of the measurementsubject 90, that is, the combination of the “torso angle” and the “armposition” is specified. In other words, the orientation of themeasurement subject 90 is determined. In this example, the CPU 100functions as an orientation detection unit and determines theorientation of the measurement subject 90 based on the outputs (theabove-described average values <α_(x)>, <α_(y)>, and <α_(z)> aredesirable) of the acceleration sensor 34. Accordingly, the orientationof the measurement subject can be detected easily.

With the blood pressure monitor 1, in order to express the orientationof the measurement subject 90 specified based on the output of theacceleration sensor 34, illustrations A-1 to A-4 shown in the first rowin FIG. 8A, illustrations B-1 to B-4 shown in the first row in FIG. 8B,illustrations C-1 to C-4 shown in the first row in FIG. 8C,illustrations D-1 to D-4 shown in the first row in FIG. 8D,illustrations E-1 to E-3 shown in the first row in FIG. 8E,illustrations F-1 to F-3 shown in the first row in FIG. 8F,illustrations G-1 to G-3 shown in the first row in FIG. 8G, andillustrations H-1 to H-3 shown in the first row in FIG. 8H are preparedin advance. These illustrations A-1 to A-4, B-1 to B-4, C-1 to C-4, D-1to D-4, E-1 to E-3, F-1 to F-3, G-1 to G-3, and H-1 to H-3 correspond tocombinations obtained using the torso patterns and arm patterns asmaterials.

In these illustrations A-1 to A-4, B-1 to B-4, C-1 to C-4, D-1 to D-4,E-1 to E-3, F-1 to F-3, G-1 to G-3, and H-1 to H-3, the torso 90 b ofthe measurement subject 90 is expressed as an elongated circle. In theapproximate center in the long axis direction of the elongated circleindicating the torso 90 b, the head 90 h of the measurement subject 90is indicated by a circle and a small triangle corresponding to the nose,in a state of being overlaid slightly shifted in the short axisdirection. Also, the left upper arm 90 a around which the cuff 20 iswrapped is indicated by a circle on the left side of the elongatedcircle indicating the torso 90 b. The main body 10 attached integrallyto the cuff 20 is indicated by a rectangle.

For example, in the illustration A-1 shown in FIG. 8A, the elongatedcircle indicating the torso 90 b is extended in the horizontal directionso as to indicate that the torso angle is 0 degrees (supine position).The circle indicating the head 90 h of the measurement subject 90 isoverlaid shifted upward of the elongated circle indicating the torso 90b (note that up, down, left, and right in this paragraph indicate up,down, left, and right in FIG. 8A). The circle indicating the left upperarm 90 a is adjacent to the left of the elongated circle indicating thetorso 90 b so as to indicate “body-lateral”. The rectangle indicatingthe main body 10 is located on the upper portion of the circleindicating the left upper arm 90 a so as to indicate that the main body10 is on the front surface of the left upper arm 90 a. In theillustration A-2, the circle indicating the left upper arm 90 a isseparated from the elongated circle indicating the torso 90 b so as toindicate “body-side separated”. In the illustration A-3, the circleindicating the left upper arm 90 a is located above and to the left ofthe elongated circle indicating the torso 90 b so as to indicate“on-chest”. In the illustration A-4, the circle indicating the leftupper arm 90 a is located above and to the left of the elongated circleindicating the torso 90 b and the rectangle indicating the main body 10is located below the circle indicating the left upper arm 90 a so as toindicate “hurrah”. The other portions of the illustrations A-2 to A-4are drawn in the same manner as those of the illustration A-1.

Also, for example, in the illustration G-1 shown in FIG. 8G, theelongated circle indicating the torso 90 b is elongated in the verticaldirection so as to indicate that the torso angle is 270 degrees (leftside position). The circle indicating the head 90 h of the measurementsubject 90 is overlaid shifted to the left of the elongated circleindicating the torso 90 b (note that up, down, left, and right in thisparagraph indicate up, down, left, and right in FIG. 8G). The circleindicating the left upper arm 90 a is separated from the elongatedcircle indicating the torso 90 b so as to indicate “chest-frontseparated”. The rectangle indicating the main body 10 is located on theleft portion of the circle indicating the left upper arm 90 a so as toindicate that the main body 10 is on the front surface of the left upperarm 90 a. In the illustration G-2, the circle indicating the left upperarm 90 a is adjacent to the bottom of the elongated circle indicatingthe torso 90 b so as to indicate “body-lateral”. In the illustrationG-3, the circle indicating the left upper arm 90 a is located downwardand to the left of the elongated circle indicating the torso 90 b andthe rectangle indicating the main body 10 is located on the rightportion of the circle indicating the left upper arm 90 a so as toindicate “hurrah”. The other portions of the illustrations G-2 to G-3are drawn in the same manner as those of the illustration G-1.

In this manner, the orientation of the measurement subject 90 can beschematically indicated using the illustrations A-1 to A-4, B-1 to B-4,C-1 to C-4, D-1 to D-4, E-1 to E-3, F-1 to F-3, G-1 to G-3, and H-1 toH-3, that is, as a combination of a torso pattern indicating the “torsoangle” and an arm pattern indicating the “arm position”.

With the blood pressure monitor 1, the normalized outputs (XZcoordinates and XY coordinates) of the acceleration sensor 34 in thethird rows and the fourth rows in FIGS. 8A to 8H and the illustrationsA-1 to A-4, B-1 to B-4, C-1 to C-4, D-1 to D-4, E-1 to E-3, F-1 to F-3,G-1 to G-3, and H-1 to H-3 in the first rows are stored in a one-to-onecorrespondence as an orientation table in the memory 51. Thus, bypreparing various illustrations indicating orientations of themeasurement subject 90 in advance, image data including an illustrationof an orientation of the measurement subject 90 can be created rapidlywith simple processing during later-described display processing (stepST110 in FIG. 5).

Overall Operation

FIG. 5 illustrates an overall operation flow of the blood pressuremonitor 1.

If the measurement start switch 52B is pressed in a state in which thepower source switch 52A is on, or if a predetermined measurement timingis reached in the case of night-time blood pressure measurement, theblood pressure monitor 1 starts the blood pressure measurement. At thestart of blood pressure measurement, the CPU 100 initializes a memoryregion for processing and outputs a control signal to the valve drivingcircuit 330. Based on the control signal, the valve driving circuit 330opens the valve 33 to discharge the air in the fluid bladder 22 of thecuff 20. Next, control for adjusting the pressure sensor 31 to 0 mmHg isperformed.

When the blood pressure measurement is started, first, the CPU 100closes the valve 33 via the valve driving circuit 330, and thereafterdrives the pump 32 via the pump driving circuit 320 while monitoring thecuff pressure signal Pc using the pressure sensor 31 (and the air tube39 and the oscillation circuit 310), and thus performs control forsending air to the fluid bladder 22. Accordingly, the fluid bladder 22is inflated and the cuff pressure gradually increases (step ST101).

In the pressure increase process, in order to detect whether or notthere is external compression on the cuff 20, the CPU 100 integrates thepump driving signal Vout for the pump driving circuit 320 to acquiredata indicating the cuff compliance CL, as illustrated in FIGS. 6A and6B (step ST102).

Also, in the pressure increase process, in order to detect whether ornot there is bodily movement of the measurement subject 90 and theorientation of the measurement subject 90, the CPU 100 acquires theoutputs of the acceleration sensor 34 (step ST 103).

Also, in this example, in the pressure increase process, in order tocalculate the blood pressure values, the CPU 100 acquires the pulse wavesignal SM serving as a fluctuation component through a filter (notshown) from the cuff pressure signal Pc (step ST104).

Next, the CPU 100 functions as a blood pressure measurement unit andattempts calculation of the blood pressure values (systolic bloodpressure SBP and diastolic blood pressure DBP) and the pulse by applyinga known algorithm through the oscillometric method based on the pulsewave signal SM acquired at this time point (step ST105).

At this time point, if the blood pressure values cannot yet becalculated due to insufficient data (NO in step ST105), the processingof steps ST101 to ST105 are repeated as long as the cuff pressure hasnot reached the upper limit pressure (in the interest of safety, theupper limit pressure is set in advance to 300 mmHg, for example) (NO instep ST106).

When the blood pressure values and pulse can be thus calculated (YES instep ST105), the processing advances to step ST107, and the CPU 100detects whether or not there is external compression on the cuff 20,whether or not there is bodily movement of the measurement subject 90,and the orientation of the measurement subject 90.

Here, the CPU 100 functions as an external compression detection unitand detects whether or not there is external compression on the cuff 20based on whether or not the cuff compliance CL is at a maximum value inthe pressure increase process. Specifically, when the cuff compliance CLdecreases monotonically as illustrated in FIG. 6A in the pressureincrease process, it is determined that there is no externalcompression. On the other hand, when the cuff compliance CL has amaximum value as illustrated in FIG. 6B in the pressure increaseprocess, it is determined that there is external compression.

Also, the CPU 100 functions as a bodily movement detection unit anddetects whether or not there is bodily movement of the measurementsubject 90 based on changes in the output of the acceleration sensor 34.Specifically, in each unit period (e.g., one second or multiple seconds)in the pressure increase process, the CPU 100 obtains the average values<α_(x)>, <α_(y)>, and <α_(z)> of the outputs α_(x), α_(y), and α_(z) ofthe acceleration sensor 34 illustrated in FIG. 7. Then, when the squareroot of the sum of squares of the fluctuation amounts of theacceleration outputs α_(x), α_(y), and α_(z) in the unit period{(α_(x)-<α_(x)>)²+(α_(y)-<α_(y)>)²+(α_(z)-<α_(z)>)²}¹/2exceeds a predetermined threshold Δα, it is determined that there isbodily movement. On the other hand, if the square root of the sum of thesquares is less than or equal to the threshold Δα, it is determined thatthere is no bodily movement.

Also, the CPU 100 functions as an orientation detection unit and detectsthe orientation of the measurement subject 90 based on the outputs (theabove-described average values <α_(x)>, <α_(y)>, <α_(z)>) of theacceleration sensor 34 in the pressure increase process. Specifically,the CPU 100 determines whether or not the orientation of the measurementsubject 90 corresponds to an orientation in an illustration in one ofthe first rows (top rows) in FIGS. 8A to 8H based on the correspondencerelationship between the normalized outputs (XZ coordinates and XYcoordinates) of the acceleration sensor 34 in the third rows and fourthrows of FIGS. 8A to 8H and the illustrations A-1 to A-4, B-1 to B-4, C-1to C-4, D-1 to D-4, E-1 to E-3, F-1 to F-3, G-1 to G-3, and H-1 to H-3in the first rows, which are stored in the orientation table in thememory 51.

Next, in step ST108 in FIG. 5, the CPU 100 stores the measurementnumber, measurement time, measured blood pressure values (systolic bloodpressure SBP and diastolic blood pressure DBP), pulse, whether or notthere is external compression on the cuff 20, whether or not there isbodily movement of the measurement subject 90, and the orientation ofthe measurement subject 90, in association with each other in the memory51.

Here, the data stored in the memory 51 is accumulated for eachmeasurement of the blood pressure, as shown in the following data table(Table 1) for example. In this example, the night-time blood pressuremeasurement is performed every 30 seconds.

TABLE 1 Data table Correction according to altitude difference SystolicDiastolic Systolic Diastolic Measure- Measure- blood pressure bloodpressure Correction blood pressure blood pressure ment ment SBP DBPPulse External Bodily Orien- amount SBP′ DBP′ number time [mmHg] [mmHg][BPM] compression movement tation [mmHg] [mmHg] [mmHg] 0 23:00  125 9364 0 0 K-1 0 125 93 1 23:30  117 81 55 0 0 A-1 0 117 81 2 0:00 111 77 550 0 A-1 0 111 77 3 0:30 107 71 62 0 0 C-2 16 123 87 4 1:00 99 71 55 0 1C-2 16 115 87 5 1:30 103 65 57 0 0 B-2 8 111 73 6 2:00 105 69 54 0 0 B-28 113 77 7 2:30 111 68 62 1 0 G-2 0 111 68 8 3:00 131 85 55 0 1 A-1 0131 85 9 3:30 105 71 47 0 0 A-3 10 115 81 10 4:00 119 81 55 0 0 A-1 0119 81 11 4:30 119 81 50 0 0 B-2 8 127 89 12 5:00 118 82 54 0 0 C-2 16134 98 13 5:30 114 79 55 0 0 C-2 16 130 95 14 6:00 121 83 53 0 0 B-2 8129 91 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Here, in the “external compression” column, “1” indicates that there isexternal compression and “0” indicates that there is no externalcompression. In the “bodily movement” column, “1” indicates that thereis bodily movement and “0” indicates that there is no bodily movement.In the “orientation” column, the orientation of the measurement subject90 is indicated by the reference sign specifying an illustration in afirst row (top row) of FIGS. 8A to 8H. Note that the reference sign“K-1” in the “orientation” column indicates an orientation (e.g., anorientation corresponding to the first illustration K-1 inlater-described FIG. 15) in which the measurement subject 90 is in asitting position and the left upper arm 90 a serving as the measurementsite naturally hangs downward. Although not shown in the third andfourth rows of FIGS. 8A to 8H, the orientation K-1 is detected as thepoint at which X=0 and Z=0 in the XZ coordinate plane and is detected asthe point at which X=0 and Y=1 in the XY coordinate plane. The“correction using altitude difference” column will be described later.

Next, in step ST109 in FIG. 5, the CPU 100 functions as a blood pressurecorrection unit and corrects the measured blood pressure valuesaccording to the obtained orientation of the measurement subject 90.

As is known, the measured blood pressure values are shifted from theactual values (values in the case where the heart and the measurementsite are at the same height level) according to an altitude differencebetween the heart and the measurement site (in this example, the leftupper arm 90 a) of the measurement subject 90. In view of this, acorrection amount that is thought to be suitable due to experience isset in advance according to the obtained orientation of the measurementsubject 90, as shown in the “correction amount” column in “correctionaccording to altitude difference” of the data table (Table 1). Forexample, with the orientation “A-1”, the heart and the left upper arm 90a of the measurement subject 90 are at the same height level, andtherefore the correction amount is set to 0 [mmHg]. With the orientation“C-2”, the left upper arm 90 a is at a higher level than the heart ofthe measurement subject 90, and therefore the correction amount is setto 16 [mmHg]. Also, with the orientation “B-2”, the altitude differencebetween the heart and the left upper arm 90 a of the measurement subject90 is at a level between that of the orientation “A-1” and that of theorientation “C-2”, and therefore the correction amount is set to 8[mmHg].

Then, the CPU 100 adds the pre-set correction amount to the measuredblood pressure value according to the obtained orientation of themeasurement subject 90. For example, if the obtained orientation is“C-2”, 16 [mmHg] is added as the correction amount when the measurementblood pressure values are systolic blood pressure SBP=107 [mmHg] anddiastolic blood pressure DBP=71 [mmHg], for example. As a result, thecorrected blood pressure values are systolic blood pressure SBP′=123[mmHg] and diastolic blood pressure DBP′=87 [mmHg]. Also, if theobtained orientation is “B-2”, 8 [mmHg] is added as the correctionamount when the measurement blood pressure values are systolic bloodpressure SBP=103 [mmHg] and diastolic blood pressure DBP=65 [mmHg], forexample. As a result, the corrected blood pressure values are systolicblood pressure SBP′=111 [mmHg] and diastolic blood pressure DBP′=73[mmHg]. Note that if the obtained orientation is “A-1”, the correctionamount is 0 [mmHg], and therefore values that are the same as those ofthe systolic blood pressure SBP and the diastolic blood pressure DBP goin the “systolic blood pressure SBP” and “diastolic blood pressure DBP”columns of the data table (Table 1).

In this example, the CPU 100 additionally stores the correction amountcorresponding to the orientation and the corrected blood pressure values(systolic blood pressure SBP′ and diastolic blood pressure DBP′) in thedata table (Table 1) in the memory 51 in association with themeasurement number, the measurement time, the measured blood pressurevalues (systolic blood pressure SBP and diastolic blood pressure DBP),the pulse, whether or not there is external compression on the cuff 20,whether or not there is bodily movement of the measurement subject 90,and the orientation of the measurement subject 90.

Next, in step ST110 in FIG. 5, the CPU 100 refers to the data table(Table 1) in the memory 51, functions as a notification unit, anddisplays the blood pressure values (systolic blood pressure SBP anddiastolic blood pressure DBP) measured in this instance of measurement,the pulse, whether or not there is external compression on the cuff 20,whether or not there is bodily movement of the measurement subject 90,and the orientation of the measurement subject 90 on the display screenof the display device 50.

Finally, in step ST111 in FIG. 5, the CPU 100 performs control foropening the valve 33 via the valve driving circuit 330 and dischargingthe air in the fluid bladder 22 of the cuff 20.

Note that in the flow shown in FIG. 5, the acquisition of the cuffcompliance data, the acquisition of the output of the accelerationsensor, the acquisition of the pulse wave signal, and the calculation ofthe blood pressure values are performed in the process of increasing thepressure of the cuff 20, but there is no limitation to this. Theacquisition of the output of the acceleration sensor, the acquisition ofthe pulse wave signal, and the calculation of the blood pressure valuesmay be performed in the pressure decrease process.

Example of Display in Blood Pressure Monitor Main Body

As shown in FIGS. 9A, 9B, 10A, and 10B, a “systolic blood pressure”region 50 a for displaying the measured systolic blood pressure SBP as anumerical value, a “diastolic blood pressure” region 50 b for displayingthe measured diastolic blood pressure DBP as a numerical value, a“pulse” region 50 c for displaying the pulse as a numerical value, a“bodily movement” region 50 d for displaying whether or not there isbodily movement of the measurement subject as an illustration as bodilymovement information, a “compression” region 50 e for displaying whetheror not there is external compression on the cuff 20 as an illustrationas compression information, and an orientation region 50 f fordisplaying the orientation of the measurement subject 90 as anillustration are set on the display screen of the display device 50. Anillustration J-1 indicating that there is bodily movement is composed ofa circle m1 indicating the head of the measurement subject 90, arounded-corner rectangle (a rectangle with rounded corners) m2indicating the torso of the measurement subject 90, and a waveform markm3 indicating motion of the body. Also, the illustration J-2 indicatingthat there is external compression is obtained approximately by adding awaveform mark m4 indicating the bed surface to the illustration G-2. Theillustrations J-1 and J-2 are stored in advance in the memory 51. Notethat when there is no bodily movement, the “bodily movement” region 50 dis blank (empty) and when there is no external compression, the“compression” region 50 e is blank (empty). The illustrationcorresponding to the content (reference numeral specifying theillustration) of the “orientation” column of the data table (Table 1) isselected from among the multiple illustrations A-1 to A-4, B-1 to B-4,C-1 to C-4, D-1 to D-4, E-1 to E-3, F-1 to F-3, G-1 to G-3, and H-1 toH-3 in the first rows (top rows) in FIGS. 8A to 8H, and is displayed inthe orientation region 50 f. Accordingly, the image data including theillustration indicating the orientation of the measurement subject 90can be rapidly created with simple processing.

In the example shown in FIG. 9A, a systolic blood pressure SBP of 115mmHg, a diastolic blood pressure DBP of 87 mmHg, and a pulse of 70 BPMthat were measured in this instance of measuring are displayed asnumerical values in the “systolic blood pressure” region 50 a, the“diastolic blood pressure” region 50 b, and the “pulse” region 50 c.Also, the fact that there is bodily movement is displayed as anillustration J-1 in the “bodily movement” region 50 d. The fact thatthere is external compression is displayed as an illustration J-2 in the“compression” region 50 e. Furthermore, the orientation of themeasurement subject 90 is displayed as the illustration G-2 in theorientation region 50 f.

In the example shown in FIG. 9B, a systolic blood pressure SBP of 117mmHg, a diastolic blood pressure DBP of 81 mmHg, and a pulse of 70 BPMthat were measured in the current instance of measurement are displayedas numerical values in the “systolic blood pressure” region 50 a, the“diastolic blood pressure” region 50 b, and the “pulse” region 50 c,similarly to the example above. Also, the fact that there is no bodilymovement is displayed as a blank in the “bodily movement” region 50 d.The fact that there is no external compression is displayed as a blankin the “compression” region 50 e. Furthermore, the orientation of themeasurement subject 90 is displayed as an illustration A-1 in theorientation region 50 f.

In the example shown in FIG. 10A, similarly to the example above, asystolic blood pressure SBP of 111 mmHg, a diastolic blood pressure DBPof 68 mmHg, and a pulse of 70 BPM that were measured in the currentinstance of measurement are displayed as numerical values in the“systolic blood pressure” region 50 a, the “diastolic blood pressure”region 50 b, and the “pulse” region 50 c. Also, the fact that there isno bodily movement is displayed as a blank in the “bodily movement”region 50 d. The fact that there is external compression is displayed asthe illustration J-2 in the “compression” region 50 e. Furthermore, theorientation of the measurement subject 90 is displayed as theillustration G-2 in the orientation region 50 f.

In the example shown in FIG. 10B, similarly to the example above, asystolic blood pressure SBP of 131 mmHg, a diastolic blood pressure DBPof 85 mmHg, and a pulse of 70 BPM that were measured in the currentinstance of measurement are displayed as numerical values in the“systolic blood pressure” region 50 a, the “diastolic blood pressure”region 50 b, and the “pulse” region 50 c. Also, the fact that there isbodily movement is displayed as the illustration J-1 in the “bodilymovement” region 50 d. The fact that there is no external compression isdisplayed as a blank in the “compression” region 50 e. Furthermore, theorientation of the measurement subject 90 is displayed as theillustration A-1 in the orientation region 50 f.

Accordingly, the user can find out the blood pressure values (systolicblood pressure SBP and diastolic blood pressure DBP) and the value ofthe pulse that were measured in this instant of measurement by viewingthe numerical values in the “systolic blood pressure” region 50 a, the“diastolic blood pressure” region 50 b, and the “pulse” region 50 c onthe display screen of the display device 50. In addition to this, byviewing the illustrations in the “bodily movement” region 50 d, the“compression” region 50 e, and the orientation region 50 f, the user canintuitively understand whether or not there is bodily movement of themeasurement subject 90, whether or not there is external compression onthe cuff 20, and the orientation of the measurement subject 90 duringblood pressure measurement.

Note that in the pressure increase process shown in FIG. 5, if the cuffpressure reaches the upper limit value while the blood pressure valuescannot be calculated (YES in step ST106), the fact that an erroroccurred is stored in the memory 51 in association with the measurementtime (step ST112). In this example, “Error” is stored in the columns forthe measured blood pressure values (systolic blood pressure SBP anddiastolic blood pressure DBP) in the data table (Table 1) in the memory51. Even if this error is present, it is desirable to store thedetection results in the “external compression” column, the “bodilymovement” column, and the “orientation” column of the data table (Table1), if possible. The reason for this is that there is a possibility thatthe cause of the error is due to the external compression, bodilymovement, or orientation. Also, in step ST110 in FIG. 5, “Error” isdisplayed as character strings in the “systolic blood pressure” region50 a and the “diastolic blood pressure” region 50 b on the displayscreen of the display device 50 in this example, and illustrationsindicating the detection results are displayed in the “bodily movement”region 50 d, the “compression” region 50 e, and the orientation region50 f. In this type of case, the user can infer the cause of the error byviewing the illustrations in the “bodily movement” region 50 d, the“compression” region 50 e, and the orientation region 50 f.

Specific Method of Detecting External Compression

FIG. 14A shows change in a compliance ratio accompanying change in thecuff pressure during blood pressure measurement (pressure increaseprocess) in the case where there is no external compression on the cuff20. On the other hand, FIG. 14B shows change in a cuff compliance ratioaccompanying change in the cuff pressure during blood pressuremeasurement (pressure increase process) in the case where there isexternal compression on the cuff 20 (here, a case in which the cuff 20is placed under the torso of the measurement subject 90). Here,“compliance ratio” means the ratio between the cuff compliancecalculated during blood pressure measurement and the cuff compliance(referred to as “reference cuff compliance”) measured once as areference in a state in which there is no external compression on thecuff 20. In other words, (compliance ratio)=(cuff compliance measuredduring blood pressure measurement)/(reference cuff compliance). Thus,the compliance ratio is used to more accurately determine whether or notthere is external compression on the cuff 20. In FIGS. 14A and 14B, thedata of the compliance ratio during multiple instances of blood pressuremeasurement is denoted by respective signs at the locations of cuffpressures 10 mmHg, 30 mmHg, 50 mmHg, 70 mmHg, 90 mmHg, 110 mmHg, 130mmHg, 150 mmHg, . . . . Also, the average values of the data of themultiple instances are denoted as a line graph CLR.

As can be understood from FIG. 14A, if there is no external compressionon the cuff 20, the compliance ratio is approximately constant (exceptfor the location of the cuff pressure 10 mmHg in the low pressureregion). On the other hand, as can be understood from FIG. 14B, if thereis external compression on the cuff 20, the compliance ratio (graph CLR)has a maximum value in the intermediate pressure region (40 mmHg or moreand 120 mmHg or less) in the pressure increase process. Also, as can beunderstood from FIGS. 14A and 14B, in both the case where there is noexternal compression on the cuff 20 and the case where there is externalcompression, there is significant variation in the compliance ratio inthe low pressure region (0 mmHg to less than 40 mmHg). This is thoughtto be because the volume of the cuff 20 tends to not increase in somecases due not only to external compression but also to variation in thetensile force of wrapping the cuff 20 around the measurement site.

In view of this, in this example, taking these circumstances intoconsideration, it is determined that there is external compression onthe cuff 20 only if, in the pressure increase process, the complianceratio (CLR) is less than a first threshold REF1 (in this example, 0.7)in the low pressure region (0 mmHg to less than 40 mmHg) and thecompliance ratio CLR is greater than or equal to a second threshold REF2(in this example, 1.3) in the intermediate pressure region (40 mmHg ormore and 120 mmHg or less). It is determined that there is no externalcompression in other cases, that is, if, in the pressure increaseprocess, the compliance ratio CLR is greater than or equal to the firstthreshold REF1 (=0.7) in the low pressure region (0 mmHg to less than 40mmHg), or the compliance ratio CLR is less than the second thresholdREF2 (=1.3) in the intermediate pressure region (40 mmHg or more and 120mmHg or less). Since REF1<REF2, this determination condition matches thecondition of whether or not the compliance ratio has a maximum value inthe intermediate pressure region (40 mmHg or more and 120 mmHg or less).

In order to determine whether or not there is external compression basedon this determination condition, the CPU 100 functions as an externalcompression detection unit and executes the operation flow shown inFIGS. 11 to 13.

FIG. 11 shows portions of the overall operation flow (portions relatedto detection of external compression) in FIG. 5. That is, if bloodpressure measurement is in progress (YES in step ST201 of FIG. 11), thecuff pressure is acquired and the current cuff pressure is set as pc[i](step ST202). Here, i is an index indicating the number of instances ofprocessing, and in the first instance, i=0. Next, calculation for a pumpdriving signal (duty) is performed, and the current pump driving voltageis set as duty[i] (step ST203). Next, cuff compliance calculationprocessing (FIG. 12) for obtaining a cuff compliance is performed (stepST204).

As shown in FIG. 12, in the cuff compliance calculation processing, ifit is the first instance of processing after the start of blood pressuremeasurement (the start of pressure increase) (YES in step ST301 of FIG.12), an integration variable duty_sum for indicating an integrationvalue (integration value) of the pump driving voltage is cleared (set toduty_sum=0) (step ST302). Next, the current pump driving voltage duty[i]is added to the integration variable duty_sum (step ST303). If thecurrent cuff pressure pc[i] has not reached a predetermined value (10mmHg at first) (NO in step ST304), the processing returns to the flow ofFIG. 11 (NO in step ST205). Also, the index i indicating the number ofinstances of processing is incremented (increased by one) in step ST206of FIG. 11, and the processing of steps ST202 and ST203 and steps ST301to ST303 in FIG. 12 is repeated. When the current cuff pressure pcreaches 10 mmHg in step ST304 (when pc[i]≥10 mmHg and pc[i−1]<10 mmHg),the cuff compliance at the cuff pressure 10 mmHg is obtained asComp(0)=duty_sum/10 mmHg (step ST305). Then, the addition variableduty_sum is cleared, and the processing returns to the flow of FIG. 11(NO in step ST205). Then, the index i indicating the number of instancesof processing is incremented in step ST206 of FIG. 11, and theprocessing of steps ST202 and ST203 and steps ST301 to ST303 of FIG. 12is repeated. Then, when the current cuff pressure pc[i] reaches 30 mmHgin step ST304 (when pc[i]≥30 mmHg and pc[i−1]<30 mmHg), the cuffcompliance at the cuff pressure 30 mmHg is obtained asComp(1)=duty_sum/20 mmHg (step ST306). The processing is sequentiallyrepeated in this manner, and when the current cuff pressure pc reaches50 mmHg in step ST304 (when pc[i]≥50 mmHg and pc[i−1]<50 mmHg), the cuffcompliance at the cuff pressure 50 mmHg is obtained asComp(2)=duty_sum/20 mmHg (step ST307). Also, when the current cuffpressure pc reaches 70 mmHg in step ST304 (when pc[i]≥70 mmHg andpc[i−1]<70 mmHg), the cuff compliance at the cuff pressure 70 mmHg isobtained as Comp(3)=duty_sum/20 mmHg (step ST308). Also, when thecurrent cuff pressure pc[i] reaches 90 mmHg in step ST304 (when pc[i]>90mmHg and pc[i−1]<90 mmHg), the cuff compliance at the cuff pressure 90mmHg is obtained as Comp(4)=duty_sum/20 mmHg (step ST309). Also, whenthe current cuff pressure pc[i] reaches 110 mmHg in step ST304 (whenpc[i]≥110 mmHg and pc[i−1]<110 mmHg), the cuff compliance at the cuffpressure 110 mmHg is obtained as Comp(5)=duty_sum/20 mmHg (step ST310)Then, the addition variable duty_sum is cleared and the processingreturns to the flow of FIG. 11.

If it is determined that the blood pressure measurement has ended instep ST205 of FIG. 11 (corresponds to step ST105 of FIG. 5) (YES in stepST205), external compression existence detection processing (FIG. 13)for determining whether or not there is external compression on the cuff20 is performed (step ST207).

As shown in FIG. 13, in the external compression existence detectionprocessing, an equation is used to determine whether or not theabove-described determination condition has been satisfied. Note thatfor this determination, the CPU 100 functions in advance as a referencedata acquisition unit, and in a state in which the cuff 20 is worn on aleft upper arm 90 a and there is no external compression, the CPU 100increases the pressure in the cuff 20 and calculates the reference cuffcompliance (reference signal COMP_STD) that is to serve as a referenceat the times of the cuff pressures 10 mmHg, 30 mmHg, 50 mmHg, 70 mmHg,90 mmHg, and 110 mmHg.

Also, it is determined that there is external pressure only in the casewhere, regarding the low pressure region (0 mmHg to less than 40 mmHg),Comp(0)/COMP_STD<0.7  (Eq.0)orComp(1)/COMP_STD<0.7  (Eq.1)is established (YES in step S401) and, regarding the intermediatepressure region (40 mmHg or more and 120 mmHg or less),Comp(2)/COMP_STD≥1.3  (Eq.2)orComp(3)/COMP_STD≥1.3  (Eq.3)orComp(4)/COMP_STD≥1.3  (Eq.4)orComp(5)/COMP_STD≥1.3  (Eq.5)is established (YES in step ST402). In this case, in step ST403, acompression flag indicating that there was external compression is set.Note that although COMP_STDs in Eq. 0 to Eq. 5 are indicated by the samereference signs for the sake of simplicity, they respectively indicatethe reference cuff compliances at the times of the cuff pressures 10mmHg, 30 mmHg, 50 mmHg, 70 mmHg, 90 mmHg, and 110 mmHg (the same appliesalso to Eq. 6 to Eq. 11, which will be described next).

On the other hand, it is determined that there is no externalcompression in the case where, regarding the low pressure region (0 mmHgto less than 40 mmHg),Comp(0)/COMP_STD≥0.7  (Eq.6)orComp(1)/COMP_STD≥0.7  (Eq.7)is established (NO in step ST401), or, regarding the intermediatepressure region (40 mmHg or more and 120 mmHg or less),Comp(2)/COMP_STD<1.3  (Eq.8)orComp(3)/COMP_STD<1.3  (Eq.9)orComp(4)/COMP_STD<1.3  (Eq.10)orComp(5)/COMP_STD<1.3  (Eq.11)is established (NO in step ST402). In this case, in step ST404, a nocompression flag indicating that there was no external compression isset.

When the compression flag is set in step ST403, “1”, which indicatesthat there is external compression in the current instance of bloodpressure measurement, is stored in the “external compression” column ofthe above-described data table (Table 1). On the other hand, when the nocompression flag is set in step ST404, “0”, which indicates that thereis no external compression in the current instance of blood pressuremeasurement, is stored in the “external compression” column of the datatable (Table 1).

Thereafter, the processing returns to the flow of FIG. 11, and if thereis external compression (YES in step ST208), compression information(e.g., the illustration J-2 shown in FIGS. 9A and 10B) indicating thatthere was external compression in the present instance of blood pressuremeasurement is displayed in step ST209 (corresponds to step ST110 ofFIG. 5).

If it is determined whether or not there is external compression basedon the above-described determination conditions in this way, it ispossible to more accurately determine whether or not there is externalcompression on the cuff 20.

Example of Display on Hospital Terminal

FIG. 3 shows a block configuration of a hospital terminal 200 that cancommunicate with the blood pressure monitor 1 via a network 900. Thehospital terminal 200 is composed of a commercially-available personalcomputer, includes a main body 200M, and includes a control unit 210composed of a CPU, a memory 220 including a RAM (Random Access Memory)and a ROM (Read Only Memory), an operation unit 230 including a keyboardand a mouse, a display device 240 composed of an LCD, and acommunication unit 290 for performing communication via the network 900,all of which are mounted in the main body 200M.

FIGS. 15 to 17 illustrate images displayed on the display screen of thedisplay device 240 based on the image data received by the hospitalterminal 200 from the blood pressure monitor 1 via the communicationunit 290.

For example, as shown in FIG. 15, the “measurement orientation” region240 a indicating the orientation of the measurement subject 90 duringblood pressure measurement, the “bodily movement/compression” region 240b indicating whether or not there is bodily movement of the measurementsubject 90 or compression, a blood pressure/pulse region 240 cindicating the measured blood pressure values or the corrected bloodpressure values, and a legend region 240 d indicating a legend ofreference signs displayed on the blood pressure/pulse region 240 c areset on the display screen of the display device 240.

In the “measurement orientation” region 240 a, the illustrations K-1,A-1, C-2, . . . , which correspond to the reference numerals “K-1”,“A-1”, “C-2”, . . . stored in the above-described “orientation” columnof the data table (Table 1) are displayed in alignment with the passageof time (measurement time shown on the horizontal axis in the bloodpressure/pulse region 240 c). By viewing the illustrations of theorientations displayed in the “measurement orientation” region 240 a, adoctor serving as a user can intuitively understand the orientations ofthe measurement subject 90 during blood pressure measurement accordingto the passage of time. In the example shown in FIG. 15, it can beunderstood intuitively that the orientation of the measurement subject90 changes from K-1 to A-1, A-1, C-2, C-2, B-2, B-2, G-2, A-1, A-3, A-1,B-2, C-2, C-2, and B-2 in the period of measurement times 23:00 to 6:00.

In the “bodily movement/compression” region 240 b, the bodily movementinformation that is stored in the “bodily movement” column of the datatable (Table 1) and indicates that there is bodily movement is indicatedby a mark M-1 at the positions in the horizontal direction correspondingto the measurement times when there was bodily movement. In addition,the compression information that is stored in the “external compression”column of the data table (Table 1) and indicates that there is externalcompression is indicated by a mark M-2 at the position on the horizontalaxis corresponding to the measurement time when there was externalcompression. The mark M-1 is constituted by the words “BOD. MVMT.” beingincluded in a rectangle with rounded corners. The mark M-2 isconstituted by the word “COMP.” being included in a rectangle withrounded corners. By viewing the marks M-1 and M-2 displayed in the“bodily movement/compression” region 240 b, a doctor serving as a usercan intuitively understand that there was bodily movement of themeasurement subject 90 and that there was external compression on thecuff 20 at a specific blood pressure measurement time. In the exampleshown in FIG. 15, it can be understood intuitively that there was bodilymovement during blood pressure measurement at the blood pressuremeasurement times 1:00 and 3:00, and that there was external compressionduring blood pressure measurement at the blood pressure measurement time2:30.

In the blood pressure/pulse region 240 c, the measured blood pressurevalues (systolic blood pressure SBP and diastolic blood pressure DBP) inthe data table (Table 1) and the pulse value PR stored in the “pulse”column are displayed as line graphs in this example. By viewing theseline graphs, a user can intuitively understand the passage of time ofthe blood pressure values and the pulse of the measurement subject 90.Also, by viewing both the illustrations of the orientations displayed inthe “measurement orientation” region 240 a and the line graph of theblood pressure values displayed in the blood pressure/pulse region 240c, the user can intuitively understand the influence that theorientation, bodily movement, and external compression have on the bloodpressure value of the measurement subject 90.

Accordingly, for example, in the case of diagnosing the health state ofthe measurement subject 90, a doctor serving as a user can make adiagnosis giving consideration to the influence that the orientation,bodily movement, and external compression have on the blood pressurevalue of the measurement subject 90. Specifically, for example, if theorientation has a large influence on the blood pressure value of themeasurement subject 90, the doctor can make a diagnosis based only onthe blood pressure values measured at times when the measurement subject90 was in a specific orientation (e.g., A-1). Also, if the bodilymovement or the external compression has a large influence on the bloodpressure value of the measurement subject 90, it is possible to ignorethe blood pressure values measured when there is bodily movement and theblood pressure values measured when there is external compression, andto make a diagnosis based only on the blood pressure values measuredwhen there is no bodily movement and no external compression.

As shown in FIG. 16, in the blood pressure/pulse region 240 c, thecorrected blood pressure values (systolic blood pressure SBP′ anddiastolic blood pressure DBP′) in the data table (Table 1) may bedisplayed as line graphs instead of the measured blood pressure values(systolic blood pressure SBP and diastolic blood pressure DBP) in thedata table (Table 1). Accordingly, by viewing both the illustrations ofthe orientations displayed in the “measurement orientation” region 240 aand the line graph of the corrected blood pressure values displayed inthe blood pressure/pulse region 240 c, a doctor serving as a user canintuitively understand whether or not the blood pressure values of themeasurement subject 90 have been appropriately corrected according tothe orientations of the measurement subject 90 during blood pressuremeasurement.

Also, as shown in FIG. 17, the corrected blood pressure values (systolicblood pressure SBP′ and diastolic blood pressure DBP′) in the data table(Table 1) may be displayed along with the measured blood pressure values(systolic blood pressure SBP and diastolic blood pressure DBP) in thedata table (Table 1) as line graphs in the blood pressure/pulse region240 c. Accordingly, by viewing the illustrations of the orientationsdisplayed in the “measurement orientation” region 240 a and the linegraphs of the uncorrected and corrected blood pressure values displayedin the blood pressure/pulse region 240 c, a doctor serving as a user canmore intuitively understand whether or not the blood pressure values ofthe measurement subject 90 were corrected appropriately according to theorientation of the measurement subject 90 during blood pressuremeasurement.

Modified Examples

In the example above, as shown in FIGS. 8A to 8H, the orientations ofthe measurement subject 90 are detected as combinations of eight typesof “torso angles” and four or three types of “arm positions”.Furthermore, in correspondence to this, the orientations of themeasurement subject 90 are indicated using the illustrations A-1 to A-4,B-1 to B-4, C-1 to C-4, D-1 to D-4, E-1 to E-3, F-1 to F-3, G-1 to G-3,and H-1 to H-3, which are obtained by combining eight types of torsopatterns and four or three types of arm patterns. However, there is nolimitation to this, and for example, the torso angle may be detectedroughly as four types, namely 0 degrees (supine position), 90 degrees(right side position), 180 degrees (prone position), and 270 degrees(left side position), and in correspondence to this, the torso angle maybe displayed as four types of torso patterns.

Also, the “arm position” of the measurement subject 90 may be at aspecial arm position other than the four or three types ofrepresentative “arm positions” in FIGS. 8A to 8H. In this case, it isdesirable that with regard to this special arm position, the points thatare to be detected in the XZ coordinate plane in the third rows in FIGS.8A to 8H and in the XY coordinate plane in the fourth rows are defined,and the arm pattern that indicates the special arm position is prepared.For example, as shown in the “measurement orientation” region 240 a, atthe measurement time 3:30 shown in FIG. 17, the torso angle of themeasurement subject 90 is 0 degrees (supine position). In this case, theleft upper arm 90 a is in an arm position of being separated frontwardwith respect to the torso 90 b of the measurement subject 90 (beingextended approximately vertically upward). In response to this, it isdesirable that the points that are to be detected in the XZ coordinateplane in the third row and in the XY coordinate plane in the fourth rowin FIG. 8A are defined and the arm pattern indicating this arm position(in this example, illustration A-3′) is prepared.

Also, in the example above, the orientation of the measurement subject90 is indicated using the illustrations A-1 to A-4, B-1 to B-4, C-1 toC-4, D-1 to D-4, E-1 to E-3, F-1 to F-3, G-1 to G-3, and H-1 to H-3 inthe first rows (top rows) of FIGS. 8A to 8H. However, there is nolimitation to this, and the orientation of the measurement subject 90may be indicated using illustrations of another type, for example, theillustrations in the second rows of FIGS. 8A to 8H. The illustrations inthe second rows in FIGS. 8A to 8H indicate schematic views of theorientations of the measurement subject 90 from above in the verticaldirection. In the illustrations shown in the second rows, the head 90 hof the measurement subject 90 is indicated by an oval, the torso 90 b isindicated by a half-oval, and the left upper arm 90 a is indicated by arounded-corner rectangle. With this kind of illustration as well, theuser can intuitively understand the orientations of the measurementsubject 90 during blood pressure measurement according to the passage oftime.

Also, with the blood pressure monitor 1, the cuff 20 and the main body10 are constituted integrally, but there is no limitation to this.Instead, the cuff 20 and the main body 10 may be constituted separately,and may be connected via an elongated tube corresponding to the air tube39. In this case, the acceleration sensor 34 is preferably mounted in(built in) the cuff 20 so as to be able to detect the orientation of themeasurement subject 90.

As is described above, the electronic blood pressure monitor of thisdisclosure includes:

a blood pressure measurement cuff configured to be worn on a measurementsite of a measurement subject;

a blood pressure measurement unit configured to measure a blood pressurevalue of the measurement subject using the cuff; and

an external compression detection unit configured to detect whether ornot there was external compression on the cuff during the blood pressuremeasurement performed by the blood pressure measurement unit,

wherein in each predetermined pressure segment, the external compressiondetection unit calculates a cuff compliance, which is an amount of airthat is to be pumped into the cuff and is needed to increase pressure inthe cuff per unit pressure, as the pressure of the cuff is increased bythe blood pressure measurement unit during blood pressure measurement,and

the external compression detection unit determines whether or not thereis external compression on the cuff based on a change indicated by thecuff compliance in each pressure segment.

In the present specification, “during blood pressure measurement” doesnot indicate the entire period in which the blood pressure measurementcuff is worn for night-time blood pressure measurement and the like, forexample, but indicates a timing during which the blood pressure valuesof the measurement subject are measured by actually increasing orreducing the pressure of the above-described blood pressure measurementcuff.

Also, “external compression” indicates compression from the outside ofthe external circumferential surface of the blood pressure monitor thatis wrapped around the measurement site. In other words, “externalcompression” does not encompass compression from the measurement site(inner circumferential surface side of the cuff) around which the bloodpressure measurement cuff is wrapped. Typically, external compressionoccurs when the measurement subject lying on the bed surface places thecuff worn on the measurement site under the torso in the case ofnight-time blood pressure measurement. Note that “bed surface” widelyindicates a surface on which a measurement subject can lie, such as anupper surface of a bed or futon. The torso of the measurement subjectmay be wearing clothes.

With the electronic blood pressure monitor of the present disclosure, ina state in which the cuff is worn on the measurement site of themeasurement subject, a fluid is supplied to the cuff to increase thepressure, and thereby the measurement site is compressed, and the bloodpressure measurement unit performs blood pressure measurement. Accordingto this, the blood pressure value is obtained. Also, the externalcompression detection unit detects whether or not there was externalcompression on the cuff during the blood pressure measurement performedby the blood pressure measurement unit. Accordingly, the user can checkwhether or not there was external compression on the cuff during bloodpressure measurement, based on the detection result. Moreover, in eachpredetermined pressure segment, the external compression detection unitcalculates a cuff compliance, which is an amount of air that is to bepumped into the cuff and is needed to increase pressure in the cuff perunit pressure, as the pressure of the cuff is increased by the bloodpressure measurement unit during blood pressure measurement, and theexternal compression detection unit determines whether or not there isexternal compression on the cuff based on a change indicated by the cuffcompliance in each pressure segment. Accordingly, for example, if thecuff is wrapped tightly around the measurement site, it is possible toavoid a circumstance in which it is erroneously determined that there isexternal compression on the cuff due to the influence of the tension ofthe wrapping. Accordingly, it is possible to more accurately determinewhether or not there is external compression on the cuff.

With an electronic blood pressure monitor of an embodiment, the externalcompression detection unit determines whether or not there is externalcompression on the cuff according to whether or not the cuff compliancehas a maximum value with respect to pressure change of the cuff in anintermediate pressure region in which the pressure of the cuff is 40mmHg or more and 120 mmHg or less.

In the present specification, “cuff compliance” means the amount of airthat is to be pumped into the cuff, and which is needed to increase thepressure, per unit pressure of the cuff. For example,milliliters/millimeters of mercury (ml/mmHg) are used as the units.

Also, the “intermediate pressure region” (40 mmHg or more and 120 mmHgor less) is a pressure region that is set based on experiments performedby the inventor of the present invention.

In general, if there is no external compression on the cuff, the cuffcompliance gradually decreases and is saturated as the fluid is suppliedto the cuff and the pressure is increased from the low pressure region(0 mmHg to less than 40 mmHg) to the high pressure region (more than 120mmHg). The reason for this is as follows: the volume of the cuff easilyincreases in the low pressure region, and therefore a large amount ofair is needed to increase the cuff pressure, but if the tensile force ofthe cuff increases due to the cuff pressure increasing by a certainextent, the volume of the cuff substantially stops increasing. On theother hand, if the measurement subject lying on the bed surface placesthe cuff worn on the measurement site under his or her torso, the cuffis compressed from the outside (the torso and the bed surface). In thiscase, in the low pressure region (0 mmHg to less than 40 mmHg), thevolume of the cuff increases due to the cuff pressing back against thetorso of the measurement subject. Accordingly, the cuff compliancechanges gradually from a low value (varies due to the influence of thetensile force of wrapping the cuff around the measurement site) to ahigh value. On the other hand, in the high pressure region (more than120 mmHg), the torso is pressed by the upper portion of the cuff due tothe inflation of the cuff, and therefore, similarly to the case in whichthere is no external compression, the cuff compliance graduallydecreases and is saturated. As a result, in the intermediate range (40mmHg or more, 120 mmHg or less), the cuff compliance has a maximum valueaccompanying the increase of the cuff pressure. In view of this, withthe electronic blood pressure monitor of this embodiment, the externalcompression detection unit determines whether or not there is externalcompression on the cuff according to whether or not the cuff compliancehas a maximum value with respect to the pressure change of the cuff inthe intermediate pressure region (40 mmHg or more and 120 mmHg or less).Accordingly, it is possible to accurately determine whether or not thereis external compression on the cuff.

An electronic blood pressure monitor of an embodiment includes

a reference data acquisition unit configured to increase pressure in thecuff and calculate a reference cuff compliance that is to serve as areference, in a state in which the cuff is worn on the measurement siteand there is no external compression,

wherein the external compression detection unit detects a complianceratio between the cuff compliance calculated during blood pressuremeasurement and the reference cuff compliance, and

the external compression detection unit detects whether or not there isexternal compression on the cuff according to whether or not thecompliance ratio has a maximum value with respect to the pressure changeof the cuff in an intermediate pressure region in which the pressure ofthe cuff is 40 mmHg or more and 120 mmHg or less.

In the present specification, “compliance ratio” means (cuff compliancecalculated during blood pressure measurement)/(reference cuffcompliance).

With the electronic blood pressure monitor of this embodiment, thepressure is increased and the reference data acquisition unit calculatesthe reference cuff compliance that is to serve as a reference in a statein which the cuff is worn on the measurement site and there is noexternal compression. The external compression detection unit detectsthe compliance ratio between the cuff compliance calculated during bloodpressure measurement and the reference cuff compliance. Furthermore, theexternal compression detection unit detects whether or not there isexternal compression on the cuff according to whether or not thecompliance ratio has a maximum value in the pressure change of the cuffin the intermediate pressure region, in which the pressure of the cuffis 40 mmHg or more and 120 mmHg or less. Accordingly, it is possible tomore accurately determine whether or not there is external compressionon the cuff.

With an electronic blood pressure monitor of an embodiment, the externalcompression detection unit determines that there is external compressionon the cuff only when the compliance ratio is smaller than apredetermined threshold in a low pressure region in which the pressureof the cuff is less than 40 mmHg.

In the low pressure region, in which the pressure of the cuff is lessthan 40 mmHg, the volume of the cuff tends to not increase in some casesdue not only to external compression but also to variation in thetensile force of wrapping the cuff around the measurement site. In thiscase, there is a possibility that it will be erroneously determined thatthere is external compression on the cuff. In view of this, with theelectronic blood pressure monitor of this embodiment, the externalcompression detection unit determines that there is external compressionon the cuff only when the compliance ratio is smaller than apredetermined threshold in a low pressure region in which the pressureof the cuff is less than 40 mmHg. Accordingly, if the cuff is wrappedtightly around the measurement site, it is possible to avoid a situationin which it is erroneously determined that there is external compressionon the cuff due to the influence of the tensile force of the wrapping.Accordingly, it is possible to more accurately determine whether or notthere is external compression on the cuff.

An electronic blood pressure monitor of an embodiment includes a storageunit configured to store compression information indicating a result ofdetection performed by the external compression detection unit, inassociation with the blood pressure value measured by the blood pressuremeasurement unit.

With the blood pressure monitor of this embodiment, the storage unitstores the compression information indicating the result of detectionperformed by the external compression detection unit, in associationwith the blood pressure value measured by the blood pressure measurementunit. The storage content of the storage unit is read out, whereby theuser can check whether or not there was external compression on the cuffduring blood pressure measurement.

An electronic blood pressure monitor of an embodiment includes anotification unit configured to perform notification of compressioninformation indicating the result of detection performed by the externalcompression detection unit, in association with the blood pressure valuemeasured by the blood pressure measurement unit.

With the blood pressure monitor of this embodiment, the notificationunit performs notification of the compression information indicating theresult of detection performed by the external compression detectionunit, in association with the blood pressure value measured by the bloodpressure measurement unit. According to the notification content of thenotification unit, the user can find out whether or not there wasexternal compression on the cuff during blood pressure measurement.Accordingly, for example, in the case of diagnosing the health state ofthe measurement subject, a doctor serving as a user can make a diagnosisgiving consideration to the influence that the external compression hason the blood pressure value of the measurement subject. Specifically,for example, if the external compression has a large influence on theblood pressure values of the measurement subject 90, the blood pressurevalues measured when there was external compression can be ignored, anddiagnosis can be performed based on only the blood pressure valuesmeasured when there was no external compression.

Also, an electronic blood pressure monitor of an embodiment includes

a reference data acquisition unit configured to increase pressure in thecuff and calculate a reference cuff compliance that is to serve as areference, in a state in which the cuff is worn on the measurement siteand there is no external compression,

wherein the external compression detection unit detects a complianceratio between the cuff compliance calculated during blood pressuremeasurement and the reference cuff compliance, and

the external compression detection unit detects whether or not there isexternal compression on the cuff according to whether or not thecompliance ratio is smaller than a predetermined first threshold in alow pressure region in which the pressure of the cuff is less than 40mmHg and the compliance ratio is greater than or equal to apredetermined second threshold in an intermediate pressure region inwhich the pressure of the cuff is 40 mmHg or more and 120 mmHg or less.

As is clear from the foregoing description, with the electronic bloodpressure monitor of the present disclosure, a user can check whether ornot there was external compression on a cuff during blood pressuremeasurement.

The above-described embodiments are exemplary and various modificationsare possible without departing from the scope of the invention. Theabove-described multiple embodiments can be established separately, butcombinations of the embodiments are also possible. Also, the variouscharacteristics of the different embodiments can be establishedseparately, but combinations of the characteristics in the differentembodiments are also possible.

The invention claimed is:
 1. An electronic blood pressure monitor, comprising: a cuff for blood pressure measurement configured to be worn on a measurement site of a measurement subject; a display; and a programmed processor, wherein the programmed processor operates as a reference data acquisition unit to increase pressure in the cuff and calculate a reference cuff compliance that is to serve as a reference, in a state in which the cuff is worn on the measurement site and there is no external compression, the programmed processor operates as a blood pressure measurement unit to measure a blood pressure value of the measurement subject using the cuff, the programmed processor operates as an external compression detection unit to detect whether or not there was external compression on the cuff during a blood pressure measurement performed by the programmed processor operator as the blood pressure measurement unit, when operating as the external compression detection unit, the programmed processor calculates cuff compliances, each of which is an amount of air that is to be pumped into the cuff and is needed to increase pressure in the cuff per unit pressure, in every one of a plurality of pressure intervals that each has a predetermined range of pressure in a pressure increase process of the cuff during the blood pressure measurement, the programmed processor calculates a compliance ratio between each cuff compliance calculated during the blood pressure measurement and the reference cuff compliance, the programmed processor determines whether or not there is external compression on the cuff according to whether or not the cuff compliance ratios have a peak in a second pressure region in which the pressure of the cuff is 40 mmHg or more and 120 mmHg or less, and the programmed processor operates as a notification unit to output, to the display, compression information that indicates a result of determining whether or not there is external compression in correspondence with the blood pressure value, and the display is controlled by the programmed processor to display the compression information in correspondence with the blood pressure value on a display screen.
 2. The electronic blood pressure monitor according to claim 1, wherein, when operating as the external compression detection unit, the programmed processor determines that there is external compression on the cuff only when the compliance ratios have a peak in the second pressure region and when the compliance ratios in a first pressure region, in which the pressure of the cuff is 0 mmHg or more and less than 40 mmHg, are smaller than a predetermined threshold in the pressure increase process of the cuff.
 3. The electronic blood pressure monitor according to claim 1, further comprising: a storage unit including a memory and configured to store the compression information in correspondence with the blood pressure value.
 4. An electronic blood pressure monitor, comprising: a cuff for blood pressure measurement configured to be worn on a measurement site of a measurement subject; a display; and a programmed processor, wherein the programmed processor operates as a reference data acquisition unit to increase pressure in the cuff and calculate a reference cuff compliance that is to serve as a reference, in a state in which the cuff is worn on the measurement site and there is no external compression, the programmed processor operates as a blood pressure measurement unit to measure a blood pressure value of the measurement subject using the cuff, the programmed processor operates as an external compression detection unit to detect whether or not there was external compression on the cuff during a blood pressure measurement performed by the programmed processor operating as the blood pressure measurement unit, when operating as the external compression detection unit, the programmed processor calculates cuff compliances, each of which is an amount of air that is to be pumped into the cuff and is needed to increase pressure in the cuff per unit pressure, in every one of a plurality of pressure intervals that each has a predetermined range of pressure in a pressure increase process of the cuff during the blood pressure measurement, the programmed processor calculates compliance ratio between each of the cuff compliances calculated during the blood pressure measurement and the reference cuff compliance, the programmed processor determines whether or not there is external compression on the cuff according to whether or not the compliance ratios are smaller than a predetermined first threshold in a first pressure region in which the pressure of the cuff is 0 mmHg or more and less than 40 mmHg and the compliance ratios are greater than or equal to a predetermined second threshold in a second pressure region in which the pressure of the cuff is 40 mmHg or more and 120 mmHg or less, in the pressure increase process of the cuff, and the programmed processor operates as a notification unit to output, to the display, compression information that indicates a result of determining whether or not there is external compression in correspondence with the blood pressure value, and the display is controlled by the programmed processor to display the compression information in correspondence with the blood pressure value on a display screen.
 5. The electronic blood pressure monitor according to claim 4, further comprising: a storage unit including a memory and configured to store the compression information in correspondence with the blood pressure value. 